Contact resistance of a contact between a lead connector and a metallic pad on a printed circuit board becomes very important when high level of electrical current flows through the contact. High level of electrical current normally is experienced in operation of power amplifiers. Such power amplifiers are found in wireless telecommunication devices. When the contact resistance is high, the resistance causes a substantial voltage drop across the contact. More importantly, excessive contact resistance causes heat to generate in the contact area which often times causes equipment failure. The level of contact resistance is unpredictable due to variations of the contact force between the lead connector and the metallic pad. The metallic pad and the lead may be connected via a screw. The contact resistance is depended on how tight the screw is turned. If the screw, or similar clamping device, is used to clamp a heat sink to a power device for heat sinking application, it is important that the screw is adequately clamping the heat sink to the power device.
When electrical circuits are manufactured and tested in a factory, the contact resistance, or contact force, is very often overlooked. As a result, a printed circuit board after being placed in operation may fail due to high contact resistance. Therefore, there is a need for a method and apparatus for determining contact resistance of a contact in an electrical circuit.